The Samyang 14mm f/2.8 is popular with the astro-landscape crowd. I think it does best at f/4 if you want full frame. f/2.8 is fine for crop. The lens has rather impressive vignetting in addition to the moustache distortion. The astro-imaging program I attempt to use requires a reference frame image for the vignetting. This 14mm lens competes very favorably in the "most fun per dollar" category.